What Is Step Flashing and How Does It Work?
Step flashing is a waterproofing technique used where a sloped roof plane meets a vertical wall. It gets its name from the "step" pattern created by individual L-shaped pieces of metal that are woven between each course (row) of shingles as they travel up the wall.
Each piece of step flashing is typically 4 to 5 inches by 5 to 7 inches when bent into its L-shape. One leg of the "L" extends at least 4 inches up the wall surface behind the siding or wall cladding. The other leg extends at least 4 inches onto the roof surface, tucked beneath the overlapping shingle. This creates a continuous, overlapping chain of water-shedding layers that directs water away from the wall at every shingle course.
The genius of step flashing lies in its simplicity. Because each piece works independently, water that gets past one piece is caught by the next one below it. This redundancy makes step flashing one of the most reliable waterproofing methods in roofing, as long as it is installed correctly.
Step flashing is distinct from continuous flashing (a single long piece bent along the entire wall-roof intersection). While continuous flashing may seem simpler, it cannot accommodate the staggered height of shingle courses and relies on a single seal line that, if breached at any point, allows water entry along the entire wall. Step flashing avoids this vulnerability through its overlapping, course-by-course design. Understanding all types of roof flashing is essential for every Pinellas County homeowner.
Why Florida Rain Makes Proper Step Flashing Critical
Pinellas County receives 50 to 55 inches of rainfall annually, with the majority falling during intense afternoon thunderstorms from June through September. These are not gentle showers. Florida summer storms routinely deliver 1 to 3 inches of rain per hour, often accompanied by strong, gusting winds that push water sideways and upward against normal gravity flow.
This combination of heavy volume and wind-driven rain creates unique challenges for roof-wall intersections. Water does not simply flow downhill during a Florida thunderstorm. It is pushed horizontally, forced upward under shingle edges, and driven into gaps that would never see moisture in calmer climates.
Step flashing that would perform adequately for decades in the Pacific Northwest or the Midwest may fail within years in Florida if not installed to handle wind-driven rain. The key differences for Florida installation include:
- ✓Larger overlap between pieces: Florida installations should use at least 3-inch overlap between step flashing pieces, versus the 2-inch minimum common in other regions
- ✓Ice and water shield underlayment: Self-adhering membrane should be installed along all roof-wall intersections beneath the step flashing for secondary water protection
- ✓Proper counter flashing: Every step flashing installation in Florida should include counter flashing to prevent wind-driven rain from getting behind the step flashing from above
- ✓Kickout flashing at every termination: Florida building code requires kickout flashings, and they are absolutely essential for preventing wall damage during heavy storms
- ✓Corrosion-resistant materials: Salt air from the Gulf of Mexico requires aluminum or copper materials rather than galvanized steel for long-term durability
Improperly installed step flashing is a leading contributor to roof leaks in Pinellas County. The intersection where roof meets wall concentrates water flow and creates opportunities for wind-driven penetration that simply do not exist on open roof planes.
Step Flashing Materials: Aluminum, Galvanized Steel, and Copper
The material you choose for step flashing affects durability, cost, appearance, and performance in Pinellas County conditions. Each material has distinct properties that make it more or less suitable for Florida coastal environments.
Aluminum Step Flashing
Aluminum is the most commonly used and widely recommended step flashing material for Pinellas County. It forms a natural oxide layer that resists salt-air corrosion, making it ideal for properties near the Gulf of Mexico. Aluminum step flashing is lightweight, easy to cut and bend on-site, and available in pre-formed pieces as well as flat stock that can be custom-formed.
Pre-painted aluminum step flashing comes in a variety of colors to match common roofing and siding tones. The factory-applied paint adds an extra layer of weather protection and improves aesthetics where flashing edges are visible. Standard aluminum step flashing is .019 inches thick, which is sufficient for most residential applications.
Galvanized Steel Step Flashing
Galvanized steel step flashing is stronger and more rigid than aluminum. It holds its shape well and resists denting from foot traffic or debris impact. The zinc coating provides corrosion protection, but this protection has limits in Florida coastal environments.
The primary concern with galvanized steel in Pinellas County is that salt air accelerates zinc depletion. Once the zinc coating is exhausted, the underlying steel rusts rapidly. For homes within 5 miles of the Gulf shoreline, which includes most of the Pinellas County peninsula, galvanized steel is not the best choice. For inland properties in the Tampa Bay area, it can perform adequately for 15 to 20 years.
Copper Step Flashing
Copper is the premium choice for step flashing. It is naturally resistant to corrosion, antimicrobial (resisting algae and mold growth), and can last 50 years or more. Over time, copper develops a distinctive green patina that many homeowners find attractive, particularly on Spanish-style tile roofs common in Pinellas County.
Copper step flashing costs three to five times more than aluminum. It also requires careful installation to avoid galvanic corrosion when in contact with dissimilar metals. Copper nails must be used with copper flashing, and copper should not directly contact galvanized surfaces or pressure-treated lumber. For high-end homes and historic properties, copper step flashing is an excellent investment.
| Material | Cost/Linear Ft (Installed) | FL Lifespan | Salt-Air Rating | Best For |
|---|---|---|---|---|
| Aluminum | $8 - $12 | 20 - 30 years | Excellent | Most Pinellas homes |
| Galvanized Steel | $8 - $10 | 15 - 20 years | Moderate | Inland properties only |
| Copper | $12 - $25 | 50+ years | Outstanding | High-end / tile roofs |
Step-by-Step: How Step Flashing Is Installed
Understanding the proper installation process helps homeowners evaluate contractor quality and recognize potential issues. Here is how experienced Pinellas County roofers install step flashing:
- 1Prepare the Wall Surface: If working on an existing structure, the bottom courses of siding, stucco trim, or wall cladding are carefully removed to expose the wall sheathing and any existing flashing. The wall surface is inspected for rot, moisture damage, and structural integrity. Any damaged sheathing or framing is repaired before new flashing is installed.
- 2Install Underlayment: Self-adhering ice and water shield is applied along the entire roof-wall intersection. The membrane extends at least 12 inches onto the roof surface and at least 6 inches up the wall. This creates a secondary waterproof barrier beneath the step flashing.
- 3Install the First Shingle Course: Shingles are installed normally from the eave upward. The first course of shingles is laid up to where it meets the wall.
- 4Place the First Step Flashing Piece: The first L-shaped flashing piece is set with its roof leg flat on the shingle and its wall leg tight against the wall. The bottom edge of the step flashing aligns with the bottom edge of the shingle course it accompanies.
- 5Nail the Step Flashing: A single nail secures the step flashing piece to the wall, placed near the top of the wall leg. The nail is positioned high enough that the next shingle course and step flashing piece will cover it. No nails go through the roof leg, as this would penetrate the waterproof membrane.
- 6Install the Next Shingle Course: The next course of shingles is installed normally, overlapping the step flashing roof leg. The shingle covers the step flashing completely so no metal is visible.
- 7Repeat Up the Wall: Steps 4 through 6 are repeated for every shingle course along the wall. Each step flashing piece overlaps the one below it by at least 3 inches, creating a continuous watershed.
- 8Install Counter Flashing: Once all step flashing pieces are in place, counter flashing is installed over the top edges of the wall legs. Counter flashing may be tucked behind siding, embedded in a mortar joint (for stucco or masonry walls), or sealed with appropriate caulking.
- 9Install Kickout Flashing: At the bottom of the step flashing run where the roof-wall junction ends at the eave, a kickout flashing directs water outward into the gutter system rather than down behind the wall.
- 10Restore Wall Cladding: Siding, stucco trim, or other wall cladding is reinstalled over the counter flashing with appropriate gaps for drainage and sealed at the top.
Counter Flashing Integration: The Critical Second Layer
Counter flashing is the second layer of defense at a roof-wall intersection. While step flashing handles water from the roof surface, counter flashing prevents water from entering behind the step flashing from the wall side. Together, they form a two-stage system that provides far superior protection compared to either component alone.
Counter flashing is installed differently depending on the wall type:
Stucco Walls (Common in Pinellas County)
For stucco walls, counter flashing is typically a continuous metal piece with the top edge embedded behind the stucco or sealed with high-quality polyurethane sealant. Some contractors use a reglet (a groove cut into the stucco) to receive the counter flashing top edge, which is then sealed. This is the preferred method as it creates a mechanical lock rather than relying solely on sealant.
Vinyl or Aluminum Siding
For homes with vinyl or aluminum siding, counter flashing is tucked behind the siding course above the roof-wall intersection. The siding acts as the counter flashing in some cases, though dedicated counter flashing provides better protection. The key is ensuring water cannot get behind the step flashing wall legs from above.
Masonry or Brick Walls
For masonry walls, counter flashing is inserted into a mortar joint (either an existing joint that has been raked out or a saw-cut groove) and sealed with appropriate masonry caulk. The mortar joint provides excellent mechanical retention, and when properly sealed, this method can last the full life of the step flashing.
In Pinellas County, where wind-driven rain is a constant concern, counter flashing is not optional. Without it, wind can push rain behind the step flashing wall legs, defeating the entire system. Contractors who skip counter flashing or use only sealant where the step flashing meets the wall are cutting a critical corner.
Kickout Flashing: The Most Overlooked Critical Detail
Kickout flashing (also called diverter flashing) is a small but critically important piece installed at the bottom of every step flashing run. It is one of the most commonly omitted components in residential roofing, and its absence is one of the most common causes of severe wall damage in Pinellas County homes.
What Kickout Flashing Does
When water flows down a roof-wall intersection following the step flashing, it eventually reaches the bottom of the wall where the roof plane ends at the eave. Without a kickout flashing, this water simply pours off the last step flashing piece and runs directly down the face of the wall below. Over time, this concentrated water stream saturates siding, penetrates behind cladding, soaks wall sheathing, and promotes rot and mold growth inside the wall cavity.
A kickout flashing redirects this water stream outward, away from the wall face, and into the gutter. It is essentially a small metal diverter that catches the water at the transition point and flings it sideways into the drainage system.
Why Missing Kickout Flashings Cause Severe Damage
- •Water pours behind siding and soaks wall sheathing during every rainstorm
- •Wood framing and sheathing begin rotting within 1 to 3 years of exposure
- •Mold develops inside the wall cavity, often undetected until it spreads extensively
- •Exterior paint peels, stucco cracks, and siding deteriorates at the base of the wall
- •Interior drywall stains, mold, and structural damage can develop on the opposite side of the wall
- •Repair costs for wall rot and mold remediation often exceed $5,000 to $15,000
The Florida Building Code now requires kickout flashings at all roof-wall terminations. However, many older Pinellas County homes were built before this requirement and lack kickout flashings entirely. If your home has a roof-wall intersection that terminates above a section of wall, checking for kickout flashings should be a priority during your next roof maintenance inspection.
Common Step Flashing Installation Mistakes
Step flashing installation is straightforward in concept but demands precision in execution. The following mistakes are commonly seen during roof inspections in Pinellas County, and each one can lead to water damage:
Using Continuous Flashing Instead of Step Flashing
Some inexperienced contractors install a single continuous piece of bent metal along the wall-roof intersection instead of individual step flashing pieces. This looks similar from the outside but lacks the course-by-course integration with shingles that makes step flashing effective. Water can run sideways under the continuous piece and enter the wall at any point.
Insufficient Overlap Between Pieces
Each step flashing piece must overlap the one below it by at least 2 inches (3 inches recommended in Florida). Pieces that barely overlap or have gaps between them allow water to bypass the system. This is especially problematic during wind-driven rain events common in Pinellas County.
Nailing Through the Roof Leg
Nails should only secure the wall leg of step flashing. Nailing through the roof leg creates penetrations that water can follow into the roof deck. The roof leg is held in place by the weight of the overlapping shingle, not by nails.
Omitting the Kickout Flashing
As discussed above, missing kickout flashings are one of the most damaging installation errors. Every step flashing run that terminates above a wall section requires a kickout flashing to direct water into the gutter.
Sealant-Only Approach
Using only roofing cement or sealant to bridge the gap between the roof surface and wall, without actual step flashing, is a shortcut that provides temporary protection at best. Sealant cracks, separates, and fails under Florida heat cycling within 2 to 5 years, leaving the intersection completely unprotected.
Skipping Counter Flashing
Counter flashing prevents water from running behind the step flashing wall legs from above. Without it, rain running down the wall face can easily enter behind the step flashing, especially during wind-driven storms. This is a common omission that undermines the entire step flashing system.
Using Dissimilar Metals
Mixing metals (for example, using galvanized nails with copper flashing or aluminum flashing against copper gutters) causes galvanic corrosion. The resulting chemical reaction accelerates deterioration of the less noble metal, creating holes and weakened areas. Always use matching metal fasteners and avoid direct contact between dissimilar metals.
Step Flashing Cost Breakdown for Pinellas County
Step flashing costs in Pinellas County depend on the material, the length of the roof-wall intersection, the wall type (stucco, siding, masonry), and whether siding removal and replacement is needed. Here is a detailed cost breakdown for 2026:
| Component | Cost Range | Notes |
|---|---|---|
| Step Flashing (Aluminum, installed) | $8 - $12/linear ft | Materials, labor, integration with shingles |
| Step Flashing (Copper, installed) | $12 - $25/linear ft | Premium material, longest lifespan |
| Counter Flashing | $5 - $10/linear ft | Additional cost over step flashing |
| Kickout Flashing | $75 - $150 each | Pre-formed or custom-fabricated |
| Siding Removal/Replacement | $5 - $15/linear ft | Required for proper wall leg integration |
| Ice and Water Shield | $2 - $4/linear ft | Secondary waterproof membrane |
| Typical 15 ft Intersection (Complete) | $200 - $500 | Step flashing + counter + kickout |
| Full Home (Multiple Intersections) | $500 - $2,000 | 2 to 4 intersections, typical home |
Signs Your Step Flashing Needs Repair or Replacement
Step flashing is largely hidden behind siding and under shingles, making visual inspection challenging. However, there are clear warning signs that indicate step flashing has failed or is failing. Recognizing these signs early prevents extensive water damage and costly repairs.
Exterior Indicators
- ✗Peeling paint or bubbling on the wall surface near the roof-wall junction
- ✗Stucco cracking, discoloration, or efflorescence (white mineral deposits) along the roof-wall line
- ✗Visible rust stains on shingles or siding near the intersection
- ✗Gaps visible between the wall surface and flashing edges
- ✗Rotting or soft wood at the base of the wall below a roof-wall intersection (indicating missing kickout flashing)
- ✗Algae or moss growth concentrated along the roof-wall line
Interior Indicators
- ✗Water stains on walls (not ceilings) where the exterior roof meets a wall
- ✗Musty or mildew smell in rooms adjacent to roof-wall intersections
- ✗Damp drywall, peeling paint, or bubbling wallpaper on walls facing the roof junction
- ✗Visible mold growth on interior walls, especially at ceiling height
If you notice any of these signs, contact a professional roofer for an inspection. Step flashing failures often cause damage behind walls where it is not immediately visible, and the longer the issue goes unaddressed, the more expensive the repair becomes. For guidance on addressing active leaks, visit our roof leak repair guide.
Protecting Your Pinellas County Home With Proper Step Flashing
Step flashing is one of those roofing components that works silently when installed correctly and causes significant damage when it is not. For Pinellas County homeowners, where rain intensity and wind-driven moisture are constant threats, investing in quality step flashing materials and professional installation provides protection that pays for itself many times over.
Key takeaways for protecting your home:
- ✓Choose aluminum or copper step flashing for corrosion resistance in coastal air
- ✓Insist on counter flashing at every roof-wall intersection
- ✓Verify kickout flashings are installed at every termination point
- ✓Include step flashing replacement in any re-roofing project
- ✓Monitor exterior walls near roof intersections for signs of water damage
For a complete understanding of how step flashing fits into your overall roofing system, explore our comprehensive roofing guide and our detailed resource on all types of roof flashing.
Frequently Asked Questions About Step Flashing
What is step flashing and how does it work?
Step flashing consists of small, L-shaped pieces of metal installed where a sloped roof meets a vertical wall. Each piece is woven between courses of shingles, with one leg behind the wall cladding and the other under the shingles. This overlapping pattern creates a waterproof staircase that channels water away from the wall at every course.
How much does step flashing installation cost in Pinellas County?
Step flashing installation typically costs $8 to $15 per linear foot, including materials and labor. A typical 15-foot roof-wall intersection with counter flashing and kickout flashing costs $200 to $500 total. Multiple intersections on a single home may cost $500 to $2,000 combined.
What is the best step flashing material for Florida?
Aluminum is the most recommended material for Pinellas County due to its excellent corrosion resistance in salt-air environments. It is also affordable and easy to work with. Copper is the premium choice with the longest lifespan but costs significantly more. Galvanized steel is acceptable for inland properties but not recommended near the coast.
What is counter flashing and why is it needed?
Counter flashing is a second layer of metal installed over the top edges of step flashing at the wall. It prevents water from running behind the step flashing from above. In Florida, where wind-driven rain is common, counter flashing is essential for a complete waterproofing system at roof-wall intersections.
What is a kickout flashing and do I need one?
A kickout flashing directs water outward into the gutter at the bottom of a step flashing run instead of allowing it to run behind the wall cladding below. Kickout flashings are required by Florida Building Code and are absolutely essential for preventing wall rot and mold. If your home lacks kickout flashings, adding them should be a high priority.
How do I know if my step flashing needs replacement?
Warning signs include water stains on interior walls near roof-wall intersections, peeling paint or rotting wood on exterior walls at the roof junction, visible rust or corrosion on flashing edges, gaps between flashing and the wall, and any separation between step flashing pieces and shingle courses. Interior musty odors near these areas can also indicate hidden water infiltration.